Aviation fuel, kerosene, diesel, and gasoline generally contain a mixture of high-C hydrocarbons with carbon chains of 6 to 22 carbon atoms per molecule (e.g., between 6 and 16 carbon atoms per molecule). For example, Jet propellant 8 (JP-8) is a kerosene-based aviation fuel, specified in 1990 by the U.S. government as a replacement fuel for diesel-fueled vehicles. Commercial aviation uses a similar mixture under the name Jet-A, and the U.S. Navy uses a similar formula, under the name JP-5. In addition to powering aircraft and other tactical vehicles, JP-8 is also widely used to fuel heaters and generators. Thus, a strong advantage of JP-8 is its widespread existing supply infrastructure and distribution network. The use of a single fuel greatly simplifies logistics planning for military installments and operations.
Similar to JP-8, commercial fuels (e.g., diesel, kerosene, and gasoline) enjoy widespread use in transportation and auxiliary power generation. These high-C hydrocarbons have large energy densities by mass and volume. Therefore, the hydrocarbon fuels are convenient methods to store and transport energy to the end user. Developed countries have extensive distribution infrastructures that allow customers to purchase hydrocarbon fuels with ease and convenience.
Despite the effectiveness of high-C hydrocarbon fuels to supply power, low-C hydrocarbon fuels (e.g., liquefied petroleum gas (LPG)) are often needed for traditional and emerging technologies in remote regions where grid-sourced electric power is unreliable or unavailable. Such circumstances include emergency response situations, rural settings, sea expeditions, and military operations. Hence, catalytic cracking of gasoline, diesel and kerosene to LPG has drawn attention due to its distinct advantages as a portable energy source with better flexibility and higher efficiency for point-of-use devices like solid oxide fuel cells (SOFC), burners, stoves, refrigerators, or lanterns. Other LPG uses include portable back-up power, autogas, or fuel for in-field operations such as health clinics, lighting, commercial gas appliances, or primary power for small-scale applications.
Diesel generators have been employed to fill gaps left by the absence or inconsistency of grid power in rural settings. Batteries are another alternative that can be sized to a range of systems: from a pacemaker to renewable energy systems. Despite their popularity, generators and batteries exhibit significant drawbacks in the aforementioned settings; single-fuel reliance, noise pollution, exhaust emissions, and mechanical vibrations from diesel generators limit their use in close proximity with people. Inherently low energy densities in batteries (0.1-0.3 MJ/L) lead to short run times or bulky systems.
The development of SOFC capable of using low-C hydrocarbon fuel (e.g. LPG) as a feedstock has created a viable high-energy-density technology for replacing the diesel generators and batteries used to create power in remote or mobile applications. Due to the unsurpassed volumetric energy density of liquid high-C hydrocarbon fuels and the existing infrastructure for their distribution, it is preferable to transport and store gasoline, diesel and jet fuel and catalytically crack it on-site to LPG. The ideal cracking catalyst must be capable of operating without excessively coking or being poisoned by sulfur present in the feedstock, and must be capable of being regenerated at temperatures similar to the reaction temperature, preferably using only air.
Besides electricity production, developing regions and off-grid locations demand fuels for cooking and heating. Current common fuels include charcoal, animal dung, and biowaste. All of these fuels (charcoal, animal dung, biowaste) produce harmful emissions that lead to respiratory problems and, in extreme cases, premature fatalities. Sulfur emissions from burning high-C hydrocarbon fuels preclude their use for heating and cooking. A need exists to provide clean-burning low-C hydrocarbon fuels, for heating and cooking purposes, to developing and off-grid regions.